Animals must balance their energy budget despite seasonal changes in both energy availability and physiological expenditures. Immunity, in addition to growth, thermoregulation, and cellular maintenance, requires substantial energy to maintain function. Mounting an immune response requires significant energy and therefore requires using resources that could otherwise be allocated to other physiological processes. Energetic trade-offs are likely when energy demands are high. Obviously, faster growth or a more efficient conversion of feed into desirable products in an animal is both economically and ecologically important, especially in animals raised for feed production.
The recent ban of conventional cages within the EU has stimulated the development of large open farm buildings allowing egg production among free-ranging poultry as this alternative is regarded as the most ecologically friendly. Commercial egg production is commonly undertaken in large buildings where tens of thousands of egg-laying hens are housed. The activities of the hens will cause air pollution of respirable particulates (<4 μm diameter) as well as microorganisms beyond what was noted when cages were used. These particles will be inhaled causing an increase in the bioload defined as the level of biologically active components of the indoor ambient air which will require the immune system to be activated and as a consequence the energy consumption will increase and more feeding is required. When the free-ranging was introduced, it was noted that the feed conversion factor increased and it was thought to be a consequence of the poultry being more active as the indoor environment had been adapted to the new situation of farming with adequate floor space, lighting, ventilation and temperature control.
For their running or jumping performance, horses depend on their pulmonary function. It is known that frequent exposure to respiratory viral pathogens, strenuous exercise, long distance transport, and inhalation of harmful substances destroys various aspects of the pulmonary defense system and predispose performance horses to decreased performance.
The environmental factor on animal performance can also be illustrated accordingly; pigs reared in rooms that were cleaned before stocking grew 8% faster than pigs reared in rooms that were not cleaned. It has been shown that both the number of animals sharing an airspace, and the stocking density in terms of kg animal per cubic meter significantly affect the level of airborne particles, especially respirable dust particles. Thus, it is clear that the concentration of biologically active components in the indoor air—the bioload—will have an impact on animals' performance. It is not only the concentration of air borne particles but also the composition of these particles that are relevant. Mycotoxins have recently been identified as sub-micron size particles. Mycotoxines are some of the most biologically active components known causing an inflammatory response by activation of the immune system and any means to reduce the occurrence of mould and mycotoxins in the stable air would add to the reduction in the stable air bioload.
From the above follows a need to reduce the bioload of the stable air preferably through means of forcing the particles to settle on surfaces and at the same time increase the oxidative capacity of the stable air. Increased oxidation with reactive oxygen (superoxide) is the mechanism used by the immune system when combating potentially toxic compounds in the air through an inflammatory response. Such a response is not only restricted to the airways but will affect the performance of the animal and increase energy consumption. Fine particles in the air are positively charged and a negatively charged electrostatic field would not only serve as an efficient means to capture said particles forcing them to settle on surfaces with a lower electrostatic potential but in case the negatively charged electrostatic field is generated by enriching the air with electrons, the oxidative capacity of the air will also increase serving as an additional means to reduce the bioload of the ambient stable air.